The present invention relates to a sector scanning, intracavitary ultrasonic probe that is inserted into a body cavity for obtaining an ultrasonic cross-sectional image.
An intracavitary ultrasonic probe of an initial stage is designed such that ultrasonic oscillators are arranged on a line, and each of the ultrasonic oscillators transmits and receives ultrasonic waves in a direction perpendicular to that line.
A drawback encountered with this ultrasonic probe is that a range of ultrasonic wave scanning to obtain a sectional image is structurally restricted by the length of the ultrasonic oscillators arranged. Therefore, the increase of the ultrasonic wave scanning range to obtain a wider sectional image inevitably requires the ultrasonic oscillators to be arranged over the increased length, which makes it difficult to insert the probe into the body cavity.
To overcome this drawback associated with this ultrasonic probe, a sector scanning, intracavitary ultrasonic probe has been developed. The sector scanning, intracavitary ultrasonic probe has ultrasonic oscillators arrayed on an arcuate line so as to scan an area outside of and lateral to the tip of the insertion portion of the probe in a sector manner. Thus, the scanning range can be increased without the increase of the arrangement length of the ultrasonic oscillators.
In the sector scanning, intracavitary ultrasonic probe, the individual ultrasonic oscillators arrayed on the arcuate line and accommodated in the insertion portion of the probe, the insertion portion of the probe partially bulges out to present an arcuate, convex shape. Because of this shape, the probe is commonly called "a convex type".
A problem with the ultrasonic probe of the convex type is that the partial bulge of the tip of the insertion portion increases its outside dimensions, thereby increasing the pain the patient may feel while the probe is inserted for inspection purposes.
Another problem is that the probe cannot be used with a small-diameter endoscope since its treatment tool insertion channel is too small in diameter to permit the passage of the bulging part of the probe.